Electronic component mounting apparatus

ABSTRACT

The electronic component mounting apparatus includes: a tray feed section (4) for feeding an electronic component (2) to be placed; an x-axis robot (5) and a y-axis robot (6) for moving the electronic component (2) to be placed; a head section (7) for holding and moving the electronic component; a 3D sensor (8); and an image memory for storing height data as three-dimensional image data, thus enabling the positioning and the three-dimensional component configuration check of the electronic component (2) to be accomplished simultaneously in one process.

TECHNICAL FIELD

The present invention relates to an electronic component mountingapparatus for automatically mounting electronic components onto a boardsuch as a printed circuit board or a liquid crystal display or plasmadisplay panel board.

BACKGROUND ART

In electronic component mounting apparatuses, for mounting suchelectronic components as QFPs or connectors with narrow lead pitches andnarrow lead widths, it has been conventional practice to executeautomatic inspections for lead floats of components before placing thecomponents onto the printed circuit board.

U.S. Pat. No. 5,200,799 representing the closest prior art from whichthe invention proceeds discloses a system for inspecting a condition ofparts packaged on a printed-circuit board which system includes aposition detecting device to receive scattered light due to illuminationof the printed-circuit board with a laser beam and convert the receivedscattered light into a position signal. This position signal is used forobtaining luminance data and at least two height data of the parts onthe printed-circuit board. Proper height data of the parts aredetermined on the basis of the difference between the two height data.The inspection system determines the package condition by comparing thefinal height data with predetermined reference data.

Accordingly, such optical inspection system checks the presence of poorconditions of mounted parts on a substrate such as position inaccuracy,lacks, rising and soldering fault of parts packaged or installed on theprinted-circuit board.

FIGS. 9A-9D are mounting process diagrams of an electronic componentmounting apparatus according to a further prior art. In most of theprior art electronic component mounting apparatus, electronic componentswith narrow lead pitches are mounted through a sequence of processes asshown in FIGS. 9A-9D. More specifically, in a step shown in FIG. 9A, anelectronic component 2 accommodated on a tray 3 is suction-picked up bya head section 7 of the mounting apparatus. Then, in a step shown inFIG. 9B, an image of the sucked-up electronic component 2 is picked upby a positioning camera 47, and the electronic component 2 is positionedby using an image processing apparatus, by which positioning informationthereabout is obtained.

In a step shown in FIG. 9C, with the use of the positioning informationacquired in the step of FIG. 9B, the electronic component 2 is subjectedto a coplanarity check by a lead float sensor 48 of transmission type orotherwise has an image picked up at an end portion or end portion shadowof a lead by a coplanarity checking camera 49 so that the image issubjected to a coplanarity check by the image processing apparatus.

With no abnormality found as a result of this check, in a step shown inFIG. 9D, a corrective calculation for a printed circuit board 9 as wellas the electronic component 2 to be mounted thereon is executed based onthe positioning information acquired in the step of FIG. 9B. Then, theelectronic component 2 is placed to a specified position on the printedcircuit board 9.

However, with the electronic component mounting apparatus of the priorart as described above, in the case where components are mounted througha sequence of processes to be performed in the steps as shown in FIGS.9A-9D, because the positioning camera 47 in the step of FIG. 9B and thelead float sensor 48 or the coplanarity checking camera 49 in the stepof FIG. 9C are installed physically separately and spaced from eachother, there is a need of mechanically positioning the components in thestep of FIG. 9C by using positioning information acquired in the step ofFIG. 9B, so that the processes in the individual steps could not besimultaneously carried out, inevitably resulting in serial processing,while the components to be mounted need to be treated for move, stop,ascent/descent or other movements for the individual steps. As a result,including the operating time for the move, stop, ascent/descent or othermovements of the mounting components, the processing time in the stepsof FIG. 9B and FIG. 9C would have a direct effect on the whole mountingtime, such that the whole mounting time would be increased by theoperating time for those movements.This is disadvantageous.

Besides, when a coplanarity check is performed by the transmission-typelead float sensor 48 as in the step of FIG. 9C, it would be necessary toscan individually four physical edges of a component to be mounted,where the processing time therefor is usually 1 to 3 seconds or so. Thisprolonged processing would result in a great demerit in mounting a largenumber of QFPs or connectors, in particular. Meanwhile, also when acoplanarity check is carried out by using the coplanarity checkingcamera 49, a long time would be required for the coplanarity check, likethe foregoing case, on account of the focusing of the camera or thecapture of divisional images due to lack of resolution or the like. Thisalso would prolong the mounting cycle time.

SUMMARY OF INVENTION

Accordingly, an object of the present invention is to provide anelectronic component mounting apparatus which can reduce the mountingprocessing time in mounting components that require a three-dimensionalconfiguration check, such as coplanarity check, and which can ensureboth lateral and vertical pixel sizes (resolution) for picked-up imagesin the mounting of components, and further which can be flexibly adaptedto higher speed and higher resolution (higher accuracy) of the mountingprocess in the case of the mounting of narrow-pitch components such asQFPs or connectors.

In accomplishing these and other aspects, according to a first aspect ofthe present invention, there is provided an electronic componentmounting apparatus comprising:

a component feeding section for feeding an electric component to bemounted onto

a board;

a head section for holding the electronic component;

a head section-moving device for moving the head section;

a three-dimensional image-acquiring device, provided at a position belowa moving range of the head section, for performing, with a laser beam,line scanning of the component held by the head section to obtain, fromeach scanning line, positional data of a position where the component ispresent and height data of the component corresponding to the positionaldata;

an image memory for storing the height data obtained from thethree-dimensional image-acquiring device as three-dimensional imagedata; and

a control section for performing image processing for thethree-dimensional image data of the electronic component.

With this arrangement, the three-dimensional image of the mountingcomponent can be acquired by the three dimensional image-acquiringdevice, and image processing for this three-dimensional image can becarried out, by which the positioning of the electronic component andthe three-dimensional component configuration checking can beaccomplished at the same time.

As a result of this, whereas the positioning by a camera and thethree-dimensional configuration characteristic such as coplanarity checkwould be done serially (in separate processes) in the prior art as shownin FIGS. 9A-9D, simultaneous processing of the positioning and thethree-dimensional check is enabled as shown in FIGS. 10A-10C, so thatthe component mounting time can be reduced to a large extent,eventually. An explanation of the difference between the aspect of thepresent invention and the prior art shown in FIGS. 9A-9D is as follows,with reference to FIGS. 10A-10C.

FIGS. 10A-10C are mounting process diagrams in the electronic componentmounting apparatus corresponding to a more specified example of thefirst aspect of the present invention. Referring to FIGS. 10A-10C,reference numeral 2 denotes an electronic component; 3 denotes a tray onwhich the electronic component 2 is placed; 7 denotes a head section formoving the electronic component 2; 8 denotes a 3D sensor as athree-dimensional image pickup means for picking up a three-dimensionalimage; and 9 denotes a printed circuit board which is an object ontowhich the electronic component 2 is mounted.

In a step shown in FIG. 10A, the electronic component 2 is picked(sucked) up from the tray 3 by the head section 7. As the electroniccomponent 2 moves on the 3D sensor 8 along with the movement of the headsection 7 in a step shown in FIG. 10B, a three-dimensional image of abottom portion 2a of the electronic component 2 that is sucked up andmoved is captured into an image memory M1 within an image processingapparatus G1 by the movement and the scanning with a laser beam 8aemitted from the 3D sensor 8. Then, image processing on thisthree-dimensional image is performed, by which both the positioning andthe three-dimensional configuration check of the electronic component 2are accomplished. In a step shown in FIG. 10C, the electronic component2 is mounted onto the printed circuit board 9 based on positioninginformation determined by the image processing of the image processingapparatus G1.

According to a second aspect of the present invention, there is providedan electronic component mounting apparatus according to the firstaspect, wherein the control section is so arranged that thethree-dimensional image data of the electronic component obtained bylaser-beam scanning in a direction vertical to a direction in which theelectronic component is moved above the three-dimensionalimage-acquiring device is acquired into the image memory, while anoperating speed of the moving device for moving the electronic componentis made constant.

With this arrangement, in the electronic component mounting apparatus asdescribed in the first aspect, the operating speed of the moving axis ismade constant, and unnecessary stops of the component moving axis areeliminated out of the mounting operations before and after the process.Thus, the processing time in the mounting process can be reduced.

According to a third aspect of the present invention, there is providedan electronic component mounting apparatus comprising:

a moving device for moving an electronic component to be mounted onto aboard;

a polygon mirror disposed at a position below the moving device;

a semiconductor laser which emits a laser beam for the polygon mirror;

a position sensing device disposed at a position around the polygonmirror; and

an image-forming lens for forming as an image on the position sensingdevice the laser beam that has struck a bottom surface of the electroniccomponent,

wherein the semiconductor laser is so placed that its laser beam willstrike the rotating polygon mirror, being thereby reflected, and strikethe bottom surface of the electronic component that passes above thepolygon mirror, and wherein a three-dimensional image of the electroniccomponent obtained by computing data outputted by the position sensingdevice is acquired into an image memory based on a passing operation ofthe electronic component above the polygon mirror by the moving deviceand laser scanning triggered by a rotating operation of the polygonmirror, whereby a positioning of the electronic component and aconfiguration check thereof are performed with the three-dimensionalimage.

With this arrangement, the three-dimensional image of the electroniccomponent can be acquired by a three-dimensional image-acquiring devicemade up of the polygon mirror, the semiconductor position sensingdevices, the semiconductor laser and the like, by which the positioningand the three-dimensional configuration check of the electroniccomponent can be accomplished simultaneously.

According to a fourth aspect of the present invention, there is providedan electronic component mounting apparatus according to the thirdaspect, further comprising:

a moving-amount detecting circuit for calculating a moving amount of themoving device from a reference position of the moving device;

a rotation-amount detecting circuit for calculating a rotation amount ofthe polygon mirror from a reference position of the polygon mirror uponreception of a rotation-amount signal of the polygon mirror; and

a first comparing circuit for comparing the moving amount of the movingdevice and the rotation amount of the polygon mirror with each other,

wherein when a difference between the moving amount of the moving deviceand the rotation amount of the polygon mirror as a comparison resultobtained from the first comparing circuit falls within an allowablerange, the data stored in the image memory is processed as effectivedata, while when the difference does not fall within the allowablerange, the data stored in the image memory is processed as ineffectivedata.

According to a fifth aspect of the present invention, there is providedan electronic component mounting apparatus according to the third orfourth aspect, further comprising:

a moving-speed detecting circuit for calculating a moving speed of themoving device at each time;

a rotation-speed detecting circuit for calculating a rotation speed ofthe polygon mirror at each time upon reception of a rotation-amountsignal of the polygon mirror;

a second comparing circuit for comparing the moving speed of the movingdevice and the rotation speed of the polygon mirror with each other,

wherein when a difference between the moving speed of the moving deviceand the rotation speed of the polygon mirror as a comparison resultobtained from the second comparing circuit falls within an allowablerange, the data stored in the image memory is processed as effectivedata, while when the difference does not fall within the allowablerange, the data stored in the image memory is processed as ineffectivedata.

With this arrangement, in the electronic component mounting apparatus asdescribed in the third and/or fourth aspects, either one or both of themoving amount of the moving device that moves the electronic componentto be mounted as well as the rotation amount of the polygon mirror andthe moving speed of the moving device as well as the moving speed of thepolygon mirror are monitored by way of a circuit, by which the normalityof a three-dimensional image (coincidence of lateral ratio of imagewithout any partial distortions) which is acquired by scan motions ofboth the moving device and the polygon mirror under independent motionsis ensured. Thus, the accuracy and reliability of calculation resultsobtained from the processing of the three-dimensional image are ensured.

According to a sixth aspect of the present invention, there is providedan electronic component mounting apparatus according to any one of thethird through fifth aspects, further comprising:

a clock rate changing means for changing a fundamental clock rate atwhich the three-dimensional image is acquired,

wherein when a high resolution is needed for the three-dimensionalimage, the fundamental clock rate is made faster by the clock ratechanging means while the moving speed of the moving device is madeslower, and wherein when a high-speed is needed for acquiring thethree-dimensional image, the fundamental clock is made slower by theclock rate changing means while the moving speed of the moving device ismade faster.

With this arrangement, in the electronic component mounting apparatus asdescribed in any one of the third through fifth aspects, the apparatuscan be operated by changing the fundamental clock rate (frequency) foracquiring a three-dimensional image and by, in combination, acceleratingor decelerating the moving speed of the moving device at which theobject is moved. In this way, in the process of performing thepositioning and the three-dimensional component configuration check ofan electronic component in correspondence to the components to bemounted and without impairing the normality of the acquired image, theswitching between enhancing the resolution for preference forpositioning or checking accuracy, and enhancing the scanning speed forpreference for speed can be implemented with simplicity.

According to a seventh aspect of the present invention, there isprovided an electronic component mounting apparatus according to any oneof the third through sixth aspects, further comprising:

a device for calculating a distance by which the component is movedduring a time after the component is located at an image data-acquiringstart position until the component is located at a valid laser beamstart position of line scanning,

wherein taking into consideration the distance calculated by thecalculating means, positioning of the component is performed by usingthe three-dimensional image.

According to the above construction, when positioning of the componentis performed based on the calculating result carried out by thecalculating means, it can be prevented that the positioning accuracy maybe deteriorated due to variation in a shift of timing, resulting inpositioning with higher accuracy.

According to the above aspects of the present invention, the electroniccomponent mounting apparatus can reduce the mounting processing time inmounting components that require a three-dimensional configuration checksuch as coplanarity check, and which can ensure both horizontal andvertical pixel sizes (resolution) for picked-up images in the mountingof components, and further which can be flexibly adapted to higher speedand higher resolution (higher accuracy) of the mounting for the mountingof narrow-pitch components such as QFPs or connectors.

BRIEF DESCRIPTION OF DRAWINGS

These and other aspects and features of the present invention willbecome clear from the following description taken in conjunction withthe preferred embodiments thereof with reference to the accompanyingdrawings, in which:

FIG. 1 is an overall schematic diagram of an electronic componentmounting apparatus according to an embodiment of the present invention;

FIGS. 2A, 2B, 2C, 2D, 2E, and 2F are explanatory views of acquiring of athree-dimensional image in the embodiment;

FIGS. 3A, 3B, and 3C are explanatory views of the component mountingoperation in the embodiment;

FIG. 4 is a sectional view in the x-axis direction of a 3D sensor in theembodiment;

FIG. 5 is a sectional view in the y-axis direction of a 3D sensor in theembodiment;

FIG. 6 is an explanatory view of output signals from the 3D sensor inthe embodiment;

FIG. 7 is a diagram of an arrangement diagram of a main control sectionin the embodiment;

FIG. 8 is a diagram of an internal arrangement diagram of a heightcomputation circuit in the embodiment;

FIGS. 9A, 9B, 9C, and 9D are mounting process diagrams in an electroniccomponent mounting apparatus according to the prior art;

FIGS. 10A, 10B, and 10C are mounting process diagrams in the electroniccomponent mounting apparatus according to an embodiment of the presentinvention;

FIG. 11 is an explanatory view of an example of a method of measuring aheight according to the embodiment;

FIG. 12 is an explanatory view of relationship between a main controlsection and individual devices in the embodiment;

FIG. 13 is a timing chart showing timing of image-acquiring in theembodiment;

FIG. 14 is a flowchart showing operations from image-acquiring to imageprocessing in the embodiment;

FIGS. 15A, 15B, and 15C are explanatory views of an algorithm as oneexample relating to lead recognition of the component in sequentialorder;

FIGS. 16A, 16B, and 16C are explanatory views relating to a method ofmeasuring lead floating of the component;

FIG. 17 is an explanatory view of height computation of each lead of thecomponent; and

FIG. 18 is a timing chart showing the embodiment where images of aplurality of electronics components are acquired and processed.

BEST MODE FOR CARRYING OUT THE INVENTION

Before the description of the present invention proceeds, it is to benoted that like parts are designated by like reference numeralsthroughout the accompanying drawings.

Hereinbelow, an electronic component mounting apparatus showing anembodiment of the present invention is described in detail below withreference to the accompanying drawings.

FIG. 1 is an overall outline view of the electronic component mountingapparatus according to this embodiment. In FIG. 1, reference numeral 1denotes a mounting apparatus body of the electronic component mountingapparatus, 2 denotes an electronic component to be mounted by themounting apparatus (hereinafter, abbreviated as component), 3 denotes atray on which the components are placed, 4 denotes a tray feeder unit asa component feeder unit for automatically feeding the components 2placed on the tray 3, 7 denotes a head for sucking up and placing thecomponent 2 in the mounting process, 5 denotes an x-axis-side robot(hereinafter, abbreviated as x-axis robot) which is a part of an X-Yrobot serving as one example of a component or head section movingdevice and moves the head 7 along the x-axis, 6a and 6b denote ay-axis-side robot (hereinafter, abbreviated as y-axis robot) which is apart of the X-Y robot and moves the head 7 along the y-axis, 8 denotes athree-dimensional (hereinafter, abbreviated as 3D) sensor, whichacquires a height image of the component 2. Denoted by 9 is a printedcircuit board on which the component 2 is mounted.

When the component 2 placed on the tray 3 is sucked up by the head 7 andmoves along the x-axis robot 5, a 3D (height) image of the component 2is captured by the 3D sensor 8. The (height) image obtained by the 3Dsensor 8 is processed in software, thereby subjected to a 3Dconfiguration examination for the positioning, lead float or other itemsof the component 2. Then, according to the positioning information, thecomponent 2 is placed to a specified position on the printed circuitboard 9.

FIGS. 2A-2F are explanatory views of the capturing of a 3D image of theelectronic component mounting apparatus according to the presentembodiment. In FIGS. 2A-2F, reference numeral 2 denotes the componentthat is moved by the operation of the x-axis robot 5, 8 denotes thethree-dimensional sensor, 44 denotes a laser beam scanned by a polygonmirror, 45 denotes a lead which is one of the leads of the component 2and which is bent (floated) toward a side opposite to the placementsurface, and 46 denotes height data resulting from acquiring an image ofthe lead 45 by the 3D sensor 8.

FIGS. 2A-2C depict how a 3D image of the component 2 is captured into animage memory 35 through steps of moving the component 2 on the 3D sensor8, applying the laser beam 44 to the bottom surface of the component 2by a scan of the laser beam 44 in a direction vertical to the movementof the component 2 to thereby form an image of the reflection of thelaser beam 44 on a semiconductor position-sensing device, and computingoutputs of the semiconductor position-sensing device sequentially todetermine heights.

Data captured in individual horizontal lines of the image memory 35 areheight data, as viewed from the 3D sensor 8 side, of height-computedobjects located on the individual laser scanning lines (leads andpackage of the component 2 in this case). These data are as shown in theX-Y cross sectional view.

FIGS. 2D-2F depict a state of the image memory 35 at a time point whenthe component 2 has passed the 3D sensor 8. In particular, if the lead45 is floating, the height data 46 corresponding to the lead 45 out ofthe Z-W cross sectional view is of greater value, compared with theother leads. This data comparison enables an examination of 3Dconfiguration such as the lead float examination of leads.

Also, since the image memory 35 receives two-dimensional image data ofthe component 2, image processing of this information enables thepositioning of components in the same way as the image processing usingan image pickup device such as a camera, although there is a differencebetween brightness data and height data.

FIGS. 3A-3C are explanatory views of the mounting operation of theelectronic component mounting apparatus according to the presentembodiment. In FIGS. 3A-3C, reference numerals 2, 3, 4, 8, 9 denote thecomponent to be sucked up, the tray, the tray feeder unit, the 3Dsensor, and the printed circuit board on which the components are to bemounted.

In FIGS. 3A, the track represented by arrows drawn from a point A to apoint B, from the point B to a point C, and from the point C to a pointD represents a sequence of operations in which the component 2 is placedat a required position on the printed circuit board 9 through theoperations by the electronic component mounting apparatus including thesteps of: picking up the component 2 from the tray 3, allowing thecomponent 2 to pass the 3D sensor 8, thereby acquiring a 3D image of thecomponent 2 by the 3D sensor 8, performing the positioning andexamination of the component by image processing of this image data tothereby calculate and correct the placement position.

FIGS. 3B, 3C represent how the moving operations of the individualrobots in the x-axis and y-axis directions according to the track of thecomponent 2 shown by FIG. 3A are accelerated or decelerated. In thisstate, the component 2 passes through above the 3D sensor 8 during thex-axis movement acquired between the point B and the point C, where a 3Dimage is picked up. During this process, the operating speed of thex-axis robot is constant while the y-axis robot is kept stopped.

For the rest of operation, in order to minimize the total mounting time,accelerating and decelerating operations which involve temporary stopsat speed-changing points from the operation between the point A and thepoint B to the operation between the point B and the point C, and fromthe operation between the point B and the point C to the operationbetween point C and point D are eliminated so that the mountingoperation of the machine is enhanced.

Construction and function of the 3D sensor 8 are explained in detailbelow.

FIG. 4 is an arrangement view (sectional view) of the 3D sensor 8 asviewed along the x-axis, and FIG. 5 is an arrangement view (sectionalview) of the 3D sensor 8 as viewed along the y-axis. In FIGS. 4 and 5,reference numeral 5 denotes the x-axis robot, 7 denotes the head, 2denotes the sucked-up component, 10 denotes a semiconductor laser foremitting a laser beam, 11 denotes a condensing-and-shaping lens forcondensing and shaping the laser beam, 12 denotes a polygon mirror forscanning the laser beam that has impinged on the mirror, by mechanicalrotation, 13 denotes a half mirror which passes part of the laser beamtherethrough and reflects another part, and 14 denotes a mirror forreflecting light.

Further, numeral 15 denotes an F-θ lens for changing the optical path sothat the laser beam swung mechanically by the polygon mirror 12 isprojected vertically onto the component 2, which is the subject; 16a,16b denote image-forming lenses which form into images the reflection(scattered light) of the laser beam that has impinged on the component2; 17a, 17b denote semiconductor position sensing devices (hereinafter,abbreviated as PSDs) as position detecting elements on which thereflected light of the laser beam that has impinged on the component 2forms an image through the image-forming lenses 16a, 16b, where the PSDs17a, 17b each have a function of generating an electrical signalcorrelated to the position of the image-formed beam. Further, 18a, 18bdenote output signals of the PSDs 17a, 17b.

In this case, the laser beam emitted from the semiconductor laser 10 iscondensed and shaped in beam configuration by the condensing-and-shapinglens 11, then passing through the half mirror 13, being reflected by themirror 14, and impinging on the polygon mirror 12. The polygon mirror 12being in constant rotational motion, the laser beam that has impingingon the mirror surface will be swung. Further, the laser beam changed inits optical path by the F-θ lens 15 is made to vertically impinge on thecomponent 2, and the resultant reflected light is formed into an imageon each of the PSDs 17a, 17b via the image-forming lenses 16a, 16b sothat the PSDs 17a, 17b generate the output signals 18a, 18b that allowthe heights of the laser reflecting surfaces of the component 2 to bemeasured.

Further, reference numeral 19 denotes an optical sensor for detectinginput of light, 20 denotes a signal that informs the outside of the factthat light has been input to the optical sensor 19. This signal 20 willchange when the individual mirror surfaces of the polygon mirror 12 havecome to specified angles, and, as it were, corresponds to an originsignal (indicating a surface origin) of each surface of the polygonmirror 12. Additionally, for example if the polygon mirror 12 has 18surfaces, 18 signals per rotation are outputted when the polygon mirror12 has rotated to angles in equal intervals (in every 20 degrees for 18surfaces), respectively. The resulting signals are calledrotation-amount signals of the polygon mirror 12.

The 3D sensor 8 in this embodiment has two systems of PSD circuits. Thisprovision is designed primarily to compensate shortages in the case ofone system of PSD circuit where upon reflection of the laser beam on thecomponent, the reflected light may not come back to the PSD in terms ofangle. Although three or more systems may be more effective, it istechnically similar to the case of two systems, and so the descriptionis made here of the two systems.

Here, an example of a method of measuring a height of the component tobe measured by the PSDs 17a, 17b will be representatively described in acase of the PSD 17a as based on FIG. 11.

In FIG. 11, a laser beam projected on the component 2 by scanning in adirection perpendicular to the drawing sheet of FIG. 11 from the F-θlens 15 is irregularly reflected from the component 2. In this case, itis assumed that the projected point is a point A₁ of the height 0 fromthe bottom of the component 2 and a point B₁ of the height H from thebottom thereof, the scattered laser beams are formed into images by theimage-forming lens 16a, and then form images on the PSD 17a at points A₂and B₂, respectively. As a result, electromotive forces are generated atthe points A₂ and B₂, and electric currents I₁ and I₂ are taken out fromthe point C and electric currents I₃ and I₄ are taken out from the pointD. The values of the currents I₁ and I₃ are determined by resistancecomponents in proportion to a distance X_(A) between the points A₂ and Cand a distance between the points A₂ and D, while the values of thecurrents I₂ and I₄ are determined by resistance components in proportionto a distance X_(B) between the points B₂ and C and a distance betweenthe points B₂ and D. Then, when a length of the PSD 17a is L, the X_(A)and X_(B) of FIG. 11 are found by the following equations: ##EQU1##Therefore, the distance H' between the points A₂ and B₂ on the PSD 17aof FIG. 11 is determined by the following equation;

    H'=x.sub.A -x.sub.B

The above height H is determined by the determined H' on the PSD.

Next, the principle of operation in which a 3D image is formed in theelectronic component mounting apparatus according to this embodiment isexplained with reference to FIGS. 6 and 7.

FIG. 6 is an explanatory view of an output signal from the 3D sensor 8of the electronic component mounting apparatus of the presentembodiment, and FIG. 7 is an internal arrangement diagram of the maincontrol section. Referring to FIG. 6, reference numeral 2 denotes thecomponent; 5 denotes the x-axis robot; 7 denotes the head; 8 denotes the3D sensor; 18a, 18b denote the PSD outputs; 20 denotes therotation-amount signal; 21 denotes a main control section of theelectronic component mounting apparatus; 22 denotes a reference-positionsensor for informing the main control section 21 of a reference positionfor the image acquiring of a 3D image on the x-axis robot 5; 23 denotesa reference-position signal for, when the head 7 has passed thereference-position sensor 22, informing the main control section 21 ofit; and 24 denotes an encoder of a motor that moves the x-axis robot 5;and 25 denotes an encoder signal outputted by the encoder 24.

When the component 2 picked up from the tray 3 is moved by the x-axisrobot 5, the encoder 24 keeps normally giving encoder signals (AB phase,Z phase or equivalent signal) 25 to the main control section 21.Therefore, since the reference-position signal 23 is given to the maincontrol section 21 when the component 2 passes through thereference-position sensor 22, these two signals allow the relativeposition of the component 2 from the reference position on the x-axisrobot 5 to be calculated by the main control section 21.

Meanwhile, the rotation amount of the polygon mirror 12 within the 3Dsensor 8 is normally given to the main control section 21 as therotation-amount signal 20 while the polygon mirror 12 is rotating. Thus,the rotation-amount signal 20 as well as the reference-position signal23 allow the rotation amount of the polygon mirror 12 since the passthrough the reference position to be calculated.

As the rotation amount of the polygon mirror 12 increases in proportionto its speed, so the moving amount of the x-axis robot 5 increasessimilarly. In the 3D sensor 8 in this embodiment, on the other hand, itis assumed that the polygon mirror 12 will rotate and the x-axis robot 5will advance straight in the image-acquiring of the 3D image at equalspeed to that of the rotation of the polygon mirror 12. If thiscondition is disturbed, the horizontal and vertical resolutions perpixel (pixel size) of the acquired 3D image would vary responsively tospeed variations. This makes a factor of errors in measurement accuracy.Thus, in the electronic component mounting apparatus of the presentembodiment, the 3D image is acquired into the image memory 35 locatedwithin the main control section 21 by the above-constructed 3D sensor 8,while the apparatus employs the rotation-amount signal 20 of the polygonmirror 12 as well as the encoder signal 25 of the motor to monitor andcontrol the matching between the polygon mirror 12 that basicallyexecutes equal-speed rotational motion and the head 7 that is driven bythe motor such as a servo motor.

Referring to FIG. 7, reference numeral 26 denotes a moving-amountdetecting circuit for calculating a moving amount (distance) from areference position of the x-axis robot 5 upon reception of the encodersignal 25; 27 denotes a moving-speed detecting circuit for calculating amoving speed at each time of the x-axis robot 5 upon reception of theencoder signal 25; 28 denotes a rotation-amount detecting circuit forcalculating a rotation amount from the reference position of the x-axisrobot 5 upon reception of the rotation-amount signal 20 of the polygonmirror 12; 29 denotes a rotation-speed detecting circuit for computing arotation speed at each time of the polygon mirror 12 upon reception ofthe rotation-amount signal 20; 30 denotes a first comparing circuit formaking a comparison of moving amounts between the motion of the x-axisrobot 5 and the rotation of the polygon mirror; 31 denotes a secondcomparing circuit for making a comparison of moving speeds between themotion of the x-axis robot 5 and the rotation of the polygon mirror; 32,33 denote storage circuits for storing comparison, results of thecomparing circuits 30, 31, respectively; 34 denotes a processing circuitfor controlling and monitoring the whole main control section 21; 35denotes an image memory for acquiring or storing the 3D image (heightimage); 36 denotes a timing generating circuit for generating varioustypes of timing signals to acquire PSD outputs 18a, 18b delivered by the3D sensor 8; 37 denotes an interface circuit for allowing the maincontrol section 21 to receive the PSD outputs 18a, 18b; and 38 denotes aheight computation circuit for converting and correcting the PSD outputs18a, 18b into height signals.

The PSD outputs 18a, 18b generated by the 3D sensor 8 are inputted tothe main control section 21 by the interface circuit 37. The inputtedPSD outputs 18a, 18b are basically raw signals outputted by the PSDs17a, 17b. In order that the height image is processed by software-likemanner, it is necessary to perform various types of computations such asheight conversion and corrective calculations on the PSD outputs 18a,18b, and this is done by the height computation circuit 38. A signalcomputed by the height computation circuit 38 is acquired into the imagememory 35 as height data, and subjected to various types of softwareprocessing by the processing circuit 34.

The acquiring of height data into the image memory 35 is executedsequentially on the individual horizontal lines of the image memory 35.In this case, the rotation-amount signal 20 of the polygon mirror 12 isused as a synchronization signal (reference signal) for the individualpolygon surfaces.

In such a sequence of image-acquiring operation, the operation of thex-axis robot 5 (i.e., movement of components targeted forimage-acquiring) and the operation of the polygon mirror 12 are executedindependently of each other. In more detail, based on the encoder signal25, the moving amount and speed of the x-axis robot 5 are calculated bythe moving-amount detecting circuit 26 and the moving-speed detectingcircuit 27, respectively. Then, based on the rotation-amount signal 20of the polygon mirror 12, rotation-amount and -speed of the polygonmirror 12 are calculated by the rotation-amount detecting circuit 28 andthe rotation-speed detecting circuit 29, respectively. The movingamounts and speeds of the x-axis robot 5 and the polygon mirror 12 arecompared with each other by the comparing circuits 30, 31, respectively,and the comparison results are stored in the storage circuits 32, 33. Inthis way, synchronized operation between the movement of the x-axisrobot 5 and the rotation of the polygon mirror 12 is monitored andcontrolled.

As an example of the monitoring, in each of the comparing circuits 30,31, when the difference obtained from the comparison result falls withinan allowable range, the data stored in the image memory is dealt with aseffective data. When the difference does not fall within the allowablerange, the data stored in the image memory is dealt with as ineffectivedata. That is, it may be such that any comparison error larger than aspecified level is taken as an image-acquiring fault and followed by onemore method of acquiring the image, or that, by referencing thecomparison result, the 3D image in the image memory 35 is processed fornormalization, correction or other processing with software or anadditional circuit provided.

Here, one example for converting the rotation-amount of the polygonmirror 12 into the moving amount will be described below.

It is supposed that the polygon mirror 12 a dodecahedron and it is sodesigned that the component 2 is moved by 40 μm when the polygon mirror12 is rotated by 30 degrees (=360°/12). At that time, when therotation-amount of the polygon mirror 12 after the image-acquiring isstarted is 125.5 rotation, the component 2 is moved by 60,240 (μm)[=125.5(rotation)×12 (surface/rotation)×40(μm)].

In order to realize this operation in circuits, the pulse number of therotation-amount signal 20 from the polygon mirror 12 (the number of thesignals from each surface origin which is a reference point of eachsurface of the polygon mirror 12) are counted during the image-acquiringoperation. In the above example, when the polygon mirror 12 is rotatedby 125.5 rotations, the number of the surface origins are counted by1,506 [=125.5 (rotations)×12 (the numbers of the surface origins)].Therefore, when the pulse numbers of the rotation-amount signal 20 are1,506, it may be considered that the component is moved by 40 μm andthen, the rotation-amount of the polygon mirror 12 can be converted intothe moving amount.

FIG. 8 is an internal arrangement view of the height computation circuit38. Reference numeral 41 denotes an A-D converting circuit forperforming analog-to-digital conversion on the PSD outputs 18a, 18b; 42denotes a clock generating circuit; 43 denotes a clock selecting circuitas a clock rate changing means for giving a clock of one rate(frequency) to the A-D converting circuit 41 or the image memory 35 byselecting one from among a plurality of clocks generated by the clockgenerating circuit 42; 44 denotes a height converting circuit forperforming calculations on the PSD outputs 18a, 18b by the principle oftriangulation; and 45 denotes a height correcting circuit for correctingthe non-linear relation between the position of a beam formed into animage on the surfaces PSDs 17a, 17b and the position of the laser beamimpinging on the measurement object. In this case, clocks of two or morekinds of frequencies generated by the clock generating circuit 42 areselected by the clock selecting circuit 43, and the selected clocks aregiven to necessary circuits within the main control section 21, such asthe A-D converting circuit 41 and the image memory 35, which requirethese signals, while the operating speed of the x-axis robot isincreased or decreased inversely proportional to the speed of theseclocks. Thus, it becomes possible to change the resolution withoutadding any special circuit, while maintaining the horizontal andvertical pixel sizes of the acquired image (3D image). For example,assume that when A-D conversion is performed at 4 MHz and the x-axisrobot is operated at 100 mm/s, the horizontal and vertical pixel sizesare 50 μm, equal to each other. In this case, if the clock of 8 MHz isselected and given to the necessary circuits and if the x-axis robot isoperated at 50 mm/s, then the pixel size (resolution) of the image to beacquired can be a 25 μm pixel.

In this case, the data quantity per line (horizontal line) doubles,while this is the case also with the vertical direction. Therefore, anattempt to acquire an image of a doubled resolution to the samefield-of-view size would require a four times larger capacity of theimage memory 35. This depends on whether to select the enlargement ofthe image memory 35 or to restrict the field-of-view size of the imagememory 35 in use with the resolution enhanced.

Next, the relationship between individual signals and theimage-acquiring and image-processing operations performed by the maincontrol section 21 of FIGS. 7 and 8 will be described based on FIGS. 7,8, 12, and 13.

The motor is provided in the x-axis robot 5 which moves the head section7 sucking up the component 2. An AB phase signal indicating a normalmoving distance of the x-axis robot 5 and a Z phase signal indicating afixed position (a certain rotary angle of the motor) are outputted fromthe encoder attached to the motor.

On reception of both of the Z phase signal and the position detectingsensor signal from the position detecting sensor (which is constructedby a photo-sensor or Hall element etc. as an example) for detecting thereference position, the image data-acquiring operation is started.

Since the time or period after the Z phase signal and the sensor signalare received until the image data-acquiring operation is started is veryshort, as shown in FIG. 13, a sequential operation of the laser beamemission and the image data-acquiring operation is automaticallyperformed in synchronization with the rotation-amount signal indicatingthe surface origins of the polygon mirror 12 by a hardware, not by theprocessing circuit 34. In order to perform such an operation, the timinggenerating circuit 36 outputs an image data-acquiring timing. By theoutput of the image data-acquiring timing, the image data of, forinstance, 1,000 lines are acquired. In such a manner, the time foracquiring the rotation-amount signal 20 is dealt with as the referenceposition (surface origin of each surface of the polygon mirror 12), andis determined as a start reference for acquiring the image data. Forexample, when the image data of one thousand lines per component areacquired, the image-acquiring operation is automatically completed forthe component by acquiring the image data of 1,000 lines.

The two analog signals are inputted in the above manner from each of thePSD outputs 18a, 18b, and then are amplified by an amplification circuit202 as shown in FIG. 12. Thereafter, these two analog signals areanalog-digital-converted by the A-D converting circuit 41 of the heightcomputation circuit 38 via the interface circuit 37. Thereafter, theabove-described height computation is performed based on each of the twosignals which are digitalized from the PSD outputs 18a, 18b to calculatelead height positions. Here, if a value of the digitalized signal fallswithin an allowable range, the data is dealt with as the normal data tosequentially process it. If the value does not fall within the allowablerange, the data is ignored. That is, in the two PSD outputs 18a, 18b, ifone of the outputs falls within the allowable range, only the PSD outputwithin the allowable range is used. If the values of both of the PSDoutputs fall within the allowable range, an average value between thevalues of the PSD outputs is used. If both of the values of the PSDoutputs do not fall within the allowable range, the PSD outputs are notprocessed in the sequential processes to be dealt with as errorgeneration.

After the lead height data is computed in such a manner, the heightcorrection is performed by the height correcting circuit 45. This heightcorrection should be performed because of a fact that even thoughpositions of incident beams on the PSDs 17a, 17b are linearly changed,the corresponding positions on the PSDs 17a, 17b are not linearlychanged. The height correction is performed by preliminary storingtables or curved equations for correction and correcting the computedheight data based thereon, resulting in obtaining accurate height data.

The height-corrected height data is inputted into the image memorycircuit 35 while timings obtained from the timing generating circuit 36are stored as addresses.

Then, based on data stored in the storage circuit 32 as a comparisonresult in the comparing circuit 30 between the rotations-amountdetecting circuit 28 and the moving-amount detecting circuit 26, it isdecided whether or not the image data falls within an allowable range.If it does not fall within the allowable range, the image data stored inthe image memory circuit 35 is dealt with as ineffective data. If theimage data falls within the allowable range, the data stored in theimage memory circuit 35 is read out by the processing circuit 34 toperform the image processing such as the positioning of the component.

Hereinbelow, in more detail, one example of a flow of theimage-acquiring operation and the acquired image-processing operationwith respect to one of the components 2 is shown in FIG. 14 as aflowchart.

As shown in FIG. 14, firstly, the image-acquiring of the component 2 isperformed at step #60.

Next, at step #61, the positioning of the leads of the component 2 theimage of which has been acquired is performed. As the positioning,although there are various kinds of methods (algorithms), a typicalexample thereof will be described below. This positioning is preferablyperformed in the following manner. First, as shown in FIG. 15A, theinclination of the leads at one side of the quadrangular component 2such as QFP is roughly detected. Next, as shown in FIG. 15B, positionsof the two leads arbitrarily selected among the detected leads areroughly detected. Finally, as shown in FIG. 15C, the lead positions atone side of the component are detected with good accuracy based on theroughly-detected lead positions. In such a manner, when the leadpositions at the one side of the quadrangular component 2 such as QFPare detected, the remaining lead positions may be detected with goodaccuracy as shown in FIG. 15C with respect to the leads at the remainingsides, based on the detected lead positions at the one side.

Next, it is decided at step #62 whether or not the lead pitch isacceptable. If acceptable, the height computation of each lead isperformed at step #63 in the below-described manner. In the heightcomputation, as shown in FIG. 17, the height information (which is datathemselves stored in the image memory) of a plurality of pixels(corresponding to each small square in FIG. 17) around a lead endportion 204 (oblique line portions in FIG. 17) of each lead is averagedbased on the lead position information obtained at step #61 to obtainthe lead heights. The three-dimensional position of each lead isinformation (x_(i), y_(i), z_(i)) found by adding the lead heights tothe positions of the individual leads found through the positioningoperation, where i=1, . . . , n (n is a number of leads).

Next, at step #64, a virtual plane (seating plane) is calculated. Here,the virtual plane will be described below. Generally, when componentseach having a plurality of leads such as QFPs are mounted on a board, itis possible that a part of leads of the component is separated from theelectrodes of the board, which is called a lead float state. A leadfloat detection for detecting the lead float of the component beforemounting on the board is performed at step #65. When this processing isperformed in a condition where the component is sucked by a nozzle, asshown in FIG. 16A, it is possible that the component 2 is sucked up bythe nozzle 7a with the component 2 inclined. Therefore, accurate leadfloat cannot be found simply by calculating the height of each lead dueto such an inclination of the component. Then, the virtual plane whichis a contact plane on which the component is mounted is found, and adistance from the virtual distance to each lead is needed to evaluateits lead float amount. In FIG. 16A, a reference numeral 201 denotes areference plane and 200 denotes an error (H₁ -H₂) between heights of twoleads due to the inclination caused in the component 2 sucked by thenozzle 7a.

The above virtual plane 202 is a plane constructed by three leadpositions of the component 2, and a plane satisfying the following twoconditions can be served as constructing points of the virtual plane202.

(1) As shown in FIG. 16B, all lead positions are above or on the virtualplane 202.

(2) As shown in FIG. 16C, a point (gravity center-projected point) 203at which the gravity center of the component 2 is projected on thevirtual plane 202 is present within a triangle defined by three pointsof the lead positions constructing the virtual plane 202.

Next, based on the heights computed at step #63 and the virtual planefound at step #64, it is decided at step #65 whether or not the leadfloat amount falls within an allowable range. The lead float amount isfound by calculating a distance between the lead and the virtual planefound from the three-dimensional position of the lead in all of theleads. The distance means the lead float amount of each lead from thevirtual plane. If the value of the lead float amount falls within theallowable range, the image processing operation is completed. If thevalue does not fall within the allowable range, the image processingoperation is completed as lead float error generation at step #67. Ifthe lead pitch does not fall with the allowable range at step #62, theimage processing operation is completed as pitch error generation atstep #66.

Next, one example of a correcting process of correcting a shift of theimage-acquiring timing will be described below.

FIG. 12 is a diagram indicating the relationship between the maincontrol section 21 of FIG. 7 and the individual devices, in which thedetecting circuits 26-29, the comparing circuits 30, 31, the storagecircuits 32, 33, and the processing circuit 34 are shown by a singlepolygon mirror control part 200. FIG. 13 is a timing chart showing theimage-acquiring timing.

In FIGS. 12 and 13, when the component 2 is located at a specifiedposition in accordance with the movement of the head section 7, the 3Dsensor 8 outputs the position detecting sensor signal, and the polygonmirror control part 200 is in a preparing operation for acquiring theimage data at a timing of the Z phase generation that is one of theoutputs from the encoder of the motor for moving the component and thatensures a fixed position.

After the part 200 has been in the preparing operation, actual imagedata is acquired for each one line in synchronization with the detectingoperation of the surface origins of the polygon mirror 12. That is, therotation-amount signal 20 indicating the surface origins of the polygonmirror 12 is detected, and then the image acquiring is performed at thesame as laser beam emission of the semiconductor 10.

At that time, as shown in FIG. 13, there is a time lag after the headsection 7 is located at the image data-acquiring start position untilthe image data acquisition actually started. The time lag includes anamount t by which the component 2 might be moved before the imageacquiring operation because of asynchronization of the operations of thehead section 7 and the polygon mirror 12, and a delay caused as apreparing period which is a fixed time due to the setup of the circuits.

After the time lag, the image of one frame is acquired insynchronization with the polygon mirror 12.

Therefore, a distance by which the component 2 is moved after thecomponent 2 is located at the image data-acquiring start position of the3D sensor 8 until the polygon mirror 12 of the 3D sensor 8 is located ata scanning start position is found by counting the encoder outputs (ABphase) of the motor for moving the component 2 by a counting circuit 300to output the result to the processing circuit 34. Then, based on thefound result, a positioning of the component 2 is performed, resultingin preventing the positioning accuracy from being deteriorated due tovariation of the shifts of the timing. Thus, the positioning can beperformed with higher accuracy.

Although the component 2 is sucked up by the single suction nozzle ofthe head section 7 in the above embodiments, the present invention canbe applied to a case where the head section 7 has a plurality ofnozzles. In such a case where a plurality of components are respectivelysucked up by the plurality of nozzles, when positioning and componentconfiguration check is sequentially performed and, for example, imagedata of 1,000 lines per component are acquired, image data of 4,000lines are acquired with respect to four nozzles while image data of each1,000 lines are dealt with as image data of one component.

The times for positioning and the three-dimensional configuration checkare considerably greatly taken up in the processing time. However,according to the present invention, when three-dimensional images of theplurality of components sucked up by the plurality of nozzles aresequentially acquired by the 3D sensor and then the components aremounted on a board by the nozzles in order, the time of the periodrelating to the movement of the component from the component sucking-upposition to the component mounting position is made approximatelyconstant in both of a case where one component is sucked up and moved byone nozzle and a case where the plurality of components are sucked upand moved by the plurality of nozzles, resulting in obtaining greateffects, specifically, in reduction of the processing time.

As shown in FIG. 18, the sequential order of image processing can besuitably changed in the head section 7 having the plural nozzles, inconsideration with the mounting order of the components 2. That is, forexample, it is supposed that four nozzles (No. 1 through No. 4) suck upthe components 2 in this order and their image data are acquired in theimage memory circuit 35, and the components are mounted on a board bythe four nozzles in the order of No. 1 through No. 4. At that time, eachtime the image data of each component are acquired, it is decidedwhether or not the image processing of the acquired image data should beperformed in preference to the image processing of the image data ofother components. Then, the image processing of the component having thehighest priority can be performed in preference to other imageprocessing. In such a case, since the image processing is performed inthe earliest order of the mounting operation, the mounting operation canbe performed after the corresponding image processing is beingcompleted, even though the image processing of other components isperformed.

Further, as apparent from the above description, enhancing theresolution would require not only the enhancement of the clock rate butalso the decrease in the speed of the x-axis robot 5 at the same time.

In either case, to keep up with the narrowed pitch of components such asQFPs and connectors, it is indispensable to enhance the resolution ofimages, while components that can be measured with somewhat roughresolutions would be formed into images with the fastest possiblescanning. In such cases, this means for enhancing the resolution isextremely effective.

As shown above, according to the present invention, a height image isacquiring by using a three-dimensional image-acquiring device, and imageprocessing for the three-dimensional image acquired by thisthree-dimensional image-acquiring device is done. As a result, itbecomes possible to perform the positioning of electronic components tobe mounted and the three-dimensional component configuration examinationtypified by coplanarity check at the same time in one process.

Therefore, the mounting processing time can be reduced during theprocess of mounting components that require three-dimensionalconfiguration check such as coplanarity check.

Also, the operating speed of head section-moving device for moving thehead section such as x-axis or y-axis robot as an example can be madeconstant, and the movement of the component can be freed from stoppageamong the mounting operations before and after the moving operation.Besides, asynchronous two axes (a driving shaft of the headsection-moving device and a polygon mirror driving shaft) may bebasically operated mechanically. Thus, there can be provided a system inwhich the horizontal and vertical pixel sizes (resolution) can beensured by acquiring three-dimensional images with the three-dimensionalimage-acquiring device.

This also makes it possible to ensure the horizontal and vertical pixelsizes (resolution) with respect to the acquired image during thecomponent mounting.

Further, for the mounting of narrow-pitch components such as QFPs andconnectors, an image enhanced in resolution in the acquired image of thecomponent is acquired. On the other hand, for the mounting of componentsthat can be measured with somewhat rough resolution, image-acquiring canbe accomplished by fast scanning with lowered resolution (as comparedwith the case of enhanced resolution) while maintaining the normality ofpixels in the acquired image of the mounting component.

Thus, for the mounting of narrow-pitch components such as QFPs andconnectors, the electronic component mounting apparatus can be flexiblyadapted to higher speed and higher resolution (higher precision) of themounting.

Although the outputs of the encoder 24 are used for detecting a relativeposition from the reference position on the x-axis robot 5 of the headsection 7 in the embodiments, it is possible to detect the position ofthe head section 7 by directly applying a linear scale to the x-axisrobot 5.

The entire disclosure of Japanese Patent Application No. 8-100744 filedon Apr. 23, 1996, including specification, claims, drawings, and summaryare incorporated herein by reference in its entirety.

Although the present invention has been fully described in connectionwith the preferred embodiments thereof with reference to theaccompanying drawings, it is to be noted that various changes andmodifications are apparent to those skilled in the art. Such changes andmodifications are to be understood as included within the scope of thepresent invention as defined by the appended claims unless they departtherefrom.

What is claimed is:
 1. An electronic component mounting apparatuscomprising:a component feeding section (4) for feeding an electroniccomponent (2) to be mounted onto a board; a head section (7) for holdingthe electronic component (2) fed from the component feeding section (4);a head section-moving device (5,6) for moving the head section (7)holding the electronic component (2); a three-dimensionalimage-acquiring device (8), provided at a position below a moving rangeof the head section (7), for performing, with a laser beam, linescanning the component (2) held by the head section (7) to obtain, fromeach scanning line, positional data of a position where the component ispresent and height data of the component (2) corresponding to thepositional data; an image memory (35) for storing the height dataobtained from the three-dimensional image-acquiring device (8) asthree-dimensional image data; and a control section (21) for performingimage processing for the three-dimensional image data of the electroniccomponent (2), and mounting the component onto the board based on theobtained height data and the obtained positional data of the position,and result of the image processing for the three-dimensional image data.2. An electronic component mounting apparatus according to claim 1,wherein the control section is so arranged that the three-dimensionalimage data of the electronic component obtained by laser-beam scanningin a direction vertical to a direction in which the electronic componentis moved above the three-dimensional image-acquiring device is acquiredinto the image memory, while an operating speed of the moving device formoving the electronic component is made constant.
 3. An electroniccomponent mounting apparatus comprising:a moving device (5,6) for movingan electronic component (2) to be mounted onto a board; a polygon mirror(8) disposed at a position below the moving device; a semiconductorlaser (10) which emits a laser beam for the polygon mirror; a positionsensing device (17a,17b) disposed at a position around the polygonmirror; and an image-forming lens (16a,16b) for forming as an image onthe position sensing device the laser beam that has struck a bottomsurface of the electronic component, wherein the semiconductor laser isso placed that its laser beam will strike the rotating polygon mirror,being thereby reflected, and strike the bottom surface of the electroniccomponent that passes above the polygon mirror, and wherein athree-dimensional image of the electronic component obtained bycomputing data outputted by the position sensing device is acquired intoan image memory based on a passing operation of the electronic componentabove the polygon mirror by the moving device and laser scanningtriggered by a rotating operation of the polygon mirror, whereby apositioning of the electronic component and a configuration checkthereof are performed with the three-dimensional image, and thecomponent is mounted onto the board based on result of the positioningof the electronic component and the configuration check thereof.
 4. Anelectronic component mounting apparatus according to claim 3, furthercomprising:a moving-amount detecting circuit (26) for calculating amoving amount of the moving device from a reference position of themoving device; a rotation-amount detecting circuit (28) for calculatinga rotation amount of the polygon mirror from a reference position of thepolygon mirror upon reception of a rotation-amount signal of the polygonmirror; and a first comparing circuit (30) for comparing the movingamount of the moving device and the rotation amount of the polygonmirror with each other, wherein when a difference between the movingamount of the moving device and the rotation amount of the polygonmirror as a comparison result obtained from the first comparing circuitfalls within an allowable range, the data stored in the image memory isprocessed as effective data, while when the difference does not fallwithin the allowable range, the data stored in the image memory isprocessed as ineffective data.
 5. An electronic component mountingapparatus according to claim 3, further comprising:a moving-speeddetecting circuit (27) for calculating a moving speed of the movingdevice at each time; a rotation-speed detecting circuit (29) forcalculating a rotation speed of the polygon mirror at each time uponreception of a rotation-amount signal of the polygon mirror; a secondcomparing circuit (31) for comparing the moving speed of the movingdevice and the rotation speed of the polygon mirror with each other,wherein when a difference between the moving speed of the moving deviceand the rotation speed of the polygon mirror as a comparison resultobtained from the second comparing circuit falls within an allowablerange, the data stored in the image memory is processed as effectivedata, while when the difference does not fall within the allowablerange, the data stored in the image memory is processed as ineffectivedata.
 6. An electronic component mounting apparatus according to claim3, further comprising:a clock rate changing means for changing afundamental clock rate at which the three-dimensional image is acquired,wherein when a high resolution is needed for the three-dimensionalimage, the fundamental clock rate is made faster by the clock ratechanging means while the moving speed of the moving device is madeslower, and wherein when a high-speed is needed for acquiring thethree-dimensional image, the fundamental clock is made slower by theclock rate changing means while the moving speed of the moving device ismade faster.
 7. An electronic component mounting apparatus according toclaim 3, further comprising:a device (300) for calculating a distance bywhich the component is moved during a time after the component islocated at an image data-acquiring start position until the component islocated at a valid laser beam start position of line scanning, whereintaking in consideration of the distance calculated by the calculatingmeans, positioning of the component is performed by using thethree-dimensional image.
 8. An electronic component mounting apparatusaccording to claim 4, further comprising:a moving-speed detectingcircuit (27) for calculating a moving speed of the moving device at eachtime; a rotation-speed detecting circuit (29) for calculating a rotationspeed of the polygon mirror at each time upon reception of arotation-amount signal of the polygon mirror; a second comparing circuit(31) for comparing the moving speed of the moving device and therotation speed of the polygon mirror with each other, wherein when adifference between the moving speed of the moving device and therotation speed of the polygon mirror as a comparison result obtainedfrom the second comparing circuit falls within an allowable range, thedata stored in the image memory is processed as effective data, whilewhen the difference does not fall within the allowable range, the datastored in the image memory is processed as ineffective data.
 9. Anelectronic component mounting apparatus according to claim 7, furthercomprising:a clock rate changing means for changing a fundamental clockrate at which the three-dimensional image is acquired, wherein when ahigh resolution is needed for the three-dimensional image, thefundamental clock rate is made faster by the clock rate changing meanswhile the moving speed of the moving device is made slower, and whereinwhen a high-speed is needed for acquiring the three-dimensional image,the fundamental clock is made slower by the clock rate changing meanswhile the moving speed of the moving device is made faster.
 10. Anelectronic component mounting apparatus according to claim 5, furthercomprising:a clock rate changing means for changing a fundamental clockrate at which the three-dimensional image is acquired, wherein when ahigh resolution is needed for the three-dimensional image, thefundamental clock rate is made faster by the clock rate changing meanswhile the moving speed of the moving device is made slower, and whereinwhen a high-speed is needed for acquiring the three-dimensional image,the fundamental clock is made slower by the clock rate changing meanswhile the moving speed of the moving device is made faster.
 11. Anelectronic component mounting apparatus according to claim 4, furthercomprising:a device (300) for calculating a distance by which thecomponent is moved during a time after the component is located at animage data-acquiring start position until the component is located at avalid laser beam start position of line scanning, wherein taking inconsideration of the distance calculated by the calculating means,positioning of the component is performed by using the three-dimensionalimage.
 12. An electronic component mounting apparatus according to claim5, further comprising:a device (300) for calculating a distance by whichthe component is moved during a time after the component is located atan image data-acquiring start position until the component is located ata valid laser beam start position of line scanning, wherein taking inconsideration of the distance calculated by the calculating means,positioning of the component is performed by using the three-dimensionalimage.
 13. An electronic component mounting apparatus according to claim6, further comprising:a device (300) for calculating a distance by whichthe component is moved during a time after the component is located atan image data-acquiring start position until the component is located ata valid laser beam start position of line scanning, wherein taking inconsideration of the distance calculated by the calculating means,positioning of the component is performed by using the three-dimensionalimage.